VALVE GP-PRESSURE REDUCING 1400973 - Caterpillar

this procedure to troubleshoot a problem with the start/stop system. Also, use this procedure if the following diagnostic code is active or easily repeated.
Table 1
J1939 Code and Description CDL Code and Description Comments
1656-2
Engine Automatic Start Enable Switch : Erratic, Intermittent, or Incorrect 336-2
Engine Control Switch : Erratic, Intermittent, or Incorrect The two inputs from the ECS are in the opposite state.
The code is logged.
Illustration 1 g03730400
Table 2
1. Inspect the Electrical Connectors and the Wiring
A. Turn the main disconnect switch to the OFF position.
B. Thoroughly inspect the connectors. Refer to Troubleshooting, "Electrical Connectors-Inspect" for additional information.
C. Perform a 45 N (10 lb) pull test on the connector wires.
D. Check the harness for abrasions and pinch points.
Connectors and Wiring
Result: The connectors and wiring appear to be OK.
Proceed to Test Step 2.
Result: There is a problem with the connectors and/or wiring.
Repair: Repair or replace the connectors or wiring. Ensure that all the seals are properly in place and ensure that the connectors are coupled.
If the problem is not resolved, proceed to Test Step 2.
2. Check the Status of the Switch Position
A. Connect Cat® Electronic Technician (ET) to the service tool connector.
B. Use Cat ET to monitor the status of the following switch:
- Start/Run/Stop switch
C. Turn the Start/Run/Stop switch to the following positions:
- STOP position
- START position
- STOP position
Switch Status
Result: The parameter for the switch is not correct in either the STOP or the START positions.
Proceed to Test Step 3.
Result: The status for the switch is correct in both the START and STOP positions. A code for the switch is not active.
Repair: The switch appears to be operating correctly. There may be an intermittent problem in the wiring harness or connector. Refer to Troubleshooting, "Electrical Connectors - Inspect" for additional information.
If the problem is not resolved, proceed to Test Step 3.
3. Check the Wiring for an Open Circuit
A. Turn the main disconnect switch to the OFF position.
B. Disconnect the J1/P1 and the J2/P2 Electronic Control Module (ECM) connectors.
C. Remove the wires from the switch.
D. Install a jumper wire between the following wires at the switch:
- J842-BK (Black)
- R755-OR (Orange)
- R756-PK (Pink)
E. Measure the resistance between the following terminals at the P1 and P2 ECM connector:
- P1-40 and P2-92
- P1-54 and P2-92
F. Return all wiring to the original configuration.
Open Circuit
Result: The measurement indicated a short circuit. The circuit is OK.
Proceed to Test Step 4.
Result: The measurement indicated